New Redemption Grab Bag now includes an assortment of 500 cards from five (5) different expansion sets. Available at Cactus website.
Cards that are exchanged are considered "owned" by the player who has possession of them. At least that's the way the exchange with Seven Wicked Spirits was ruled. I don't see why Stalks would be any different. You should be able to set aside a Hero that you received with Stalks.
One interesting thing I find about the past discussions is that Bubbleboy has always agreed with the ruling. Suddenly he "hates" Redemption because of it.